Various compressors for use in an air conditioning system of a motor vehicle are known in the art. One such compressor includes a variable displacement compressor. The variable displacement compressor generally includes a swash plate disposed at a variable angle and at least one piston disposed in a cylinder. Each piston engages the swash plate so the angle of the swash plate as it is rotated relative to the at least one piston causes the piston to reciprocate within the cylinder. Each of the cylinders contains a refrigerant in gaseous form that is compressed by the piston within the cylinder during the rotation of the swash plate.
Many variable displacement compressors include a suction dampening device (SDD) within an inlet port of the variable displacement compressor. The SDD is configured to allow a flow of the refrigerant into the compressor while preventing the formation of vibration that may propagate throughout the remainder of the air conditioning system. The SDD typically includes a casing disposed within the inlet port, a core disposed within the casing and configured to move axially within the casing, and a spring disposed between the casing and the core that is in a pre-stressed condition such as normally compressed between the core and at least a portion of the casing, for example. A flow of the refrigerant through the inlet port causes the core to move in a direction further compressing the spring to open an orifice into the compressor, through which the refrigerant flows. Under some circumstances, the flow of the refrigerant into the inlet port may form turbulence causing the spring of the SDD to oscillate. The oscillations, especially when at a resonant frequency of the SDD, may cause vibration within the compressor to propagate throughout the air conditioning system. When the vibration reaches certain components of the air conditioning system such as the evaporator, for example, the vibration may cause undesirable noise to be generated that can be heard in a passenger compartment of the vehicle. Accordingly, the SDD typically includes a dampening feature configured to dampen the oscillating of the spring in order to prevent the incidence of noise propagation throughout the air conditioning system.
In one example, the dampening feature includes the spring of the SDD disposed at an angle with respect to a longitudinal axis of the SDD. The angled relationship causes at least a portion of the spring force to urge the core in a lateral direction against the casing, thereby forming a frictional dampening force between the core and the casing. One disadvantage of this solution is the amount of lateral force applied by the spring is dependent on the angle at which the spring is inclined, wherein an increase in the angle of inclination may frustrate normal operation of the SDD related to the opening and the closing of the orifice into the compressor.
Another exemplary SDD includes the inlet port or the casing having an asymmetrical construction such as a recess formed in a portion of an inner circumferential surface thereof. The asymmetry of the inlet port or casing causes the core to be forced in a direction toward a sidewall of the casing to provide a frictional dampening force. One disadvantage of this approach is the amount of sideways force applied to the core is dependent on a flow rate of the refrigerant passing through the casing, hence the effectiveness of the dampening effect of the SDD is minimized when the compressor is operated to have a minimized flow rate through the compressor.
It would therefore be desirable to produce a suction dampening device that efficiently minimizes noise generation in an air conditioning system independent of a flow rate of the refrigerant passing through the air conditioning system.